I'm new to this. I was given this picture set to look at, and although I was told afterwards there is an asteroid in the very bottom right (that I can't see!), I am slightly perplexed by the fairly faint object at about 10 o'clock. There is a black line through it on two pictures, but it gives the impression of some sort of movement through the entire 4 pictures. I marked it as artefact, but am unsure as to what I'm seeing.
I can only select one artefact per picture even when there are lots, so I have left the obvious ones down the middle of the picture!
You can mark more than an artifact in a picture. After entering done, it's possible to select artifact, mark another, press done.... But it's boring 😉 That's why I only (and not always !) mark those who seems interesting to avoiding misunderstanding.
It's ok that we can't see known asteroids when a picture like this is effected by other artifact (such as star bleed in this case). Computer calculations know that the asteroid is in the picture at that point, but the fact that none of us can see it help confirm what can and can't be seen by this project. In otherwords, not all tests have to have positive results to be useful. This one helps to set a range for detection when an resolution in an image set is bad.
FYI: There have been replies in other posts that having us marking artifacts is also very useful, since it helps refine the logic for identifying known artifacts. In addition, I always find it useful when I can find at least one artifact seen in all 4 frames. With those marked, it makes it easier to see other things moving with the same pattern within that set and eliminate them as artifacts. I have several times marked 4-5 different artifacts, then with those identified, finally seen an asteroid when using the number keys to cycle through the frames. For me, it was standing out now that the other moving points were surrounded by X's and not being paid attention to as much while I looked at the rest of the frame.